The manufacture of flexible polyurethane foams requires mixing components (e.g., isocyanates and polyols along with various surfactants, water, auxiliary blowing agents, catalysts, etc., depending on the foam to be produced, its density and cell structure) and causing or allowing them to react. Modern equipment or techniques involve metering components into a reaction chamber wherein they are mixed and passed onto a conveyor or in a mold where the mixture is allowed to foam. Flame retardants are metered into the reaction chamber along with the other components for mixing.
Because polyurethane foams are produced by reaction involving two main liquid components, viz., isocyanates and polyols, it is desirable for a flame retardant composition to be in the form of a liquid with low viscosity so that it will mix readily and thoroughly with the reactants at ordinary ambient temperatures.
In the manufacture of flexible foams large billets or buns of foam are produced and then set aside to cure or to complete the polymerization reaction. Temperatures within the billet from the reaction can reach 150° to 180° C. and higher. The insulating properties of the foam maintain this temperature in the interior of the billet for an extended period of time. Thus, components which are introduced into the foam, including the flame retardant components, should, if possible, be able to withstand high temperatures and not cause scorching or charring to be visible in the foam. As antioxidants are typically more expensive than the flame-retardant component, it would be highly desirable to reduce the loading of the antioxidant component to 1 wt % or less of the foam.